In engines which are currently used in aircraft, particularly aeroplanes, and function according to the operating principle of a gas turbine, outside air is compressed by means of a compressor and then supplied to a combustion chamber. In the combustion chamber, the outside air is mixed with fuel and ignited. The exhaust gas generated as a result of the combustion process is conducted over a turbine which drives a compressor, which is arranged with the turbine on a common shaft or is separated from the turbine by a gear, and also the actual propulsion unit, for example a turbofan or propeller. As the fuel, for example kerosene, which comprises a hydrocarbon mixture combusts with air in the combustion chamber of an aeroplane engine, in addition to nitrogen oxides (NOx) further combustion products, such as CO2, CO and non-burned hydrocarbons, are produced. In particular, the quantity of the nitrogen oxides formed during the combustion process depends greatly on the combustion temperature in the combustion chamber. High combustion temperatures promote the formation of nitrogen oxide. Moreover, high combustion temperatures in the combustion chamber result in a significant material load and high stresses in the engine. Particularly high combustion temperatures are achieved in the start phase of the aeroplane, during which the engine runs under full load to meet the thrust requirement. Aeroplane engines which are operated with high combustion temperatures in the combustion chamber therefore call for particularly high maintenance costs.
To reduce the nitrogen oxide emissions and to lower the thermal load, aeroplane engines should therefore be operated with the lowest possible combustion temperatures in the combustion chamber. A reduction in the combustion temperature in the combustion chamber of an aeroplane engine can be realised for example by injecting water during the combustion process. The water can either be supplied to the compressor or injected into the combustion chamber of the engine, for which the water normally has to be carried on board the aeroplane in separate tanks.
The object on which the present invention is based is to provide a system and a process which particularly efficiently enable a reduction in the combustion temperature in the combustion chamber of a engine and therefore a significant reduction in the harmful emissions during operation of the engine.